Respiratory syncytial virus (RSV) is a respiratory pathogen that produces annual epidemics of respiratory illness primarily in infants, but also in adults (Murry, A. R. and Dowell, S. F., Respiratory syncytial virus: not just for kids, Hosp. Pract. (Off. Ed.), 1997, 32(7): 87-88, 91-94, 98 passim; Centers for Disease Control and Prevention, Update: respiratory syncytial virus activity—United States, 1995-96 Season, JAMA, 1996, 275(1): 29). RSV causes bronchiolitis and exacerbates asthma and may also lead to life-threatening respiratory conditions resulting in prolonged hospitalization and death in high-risk individuals (Armstrong, D. S. and Menahem, S. J. Paediatr. Child Health, 1993, 29(4): 309-311; Fiedler, M. A. et al. J. Virol., 1996, 70(12): 9079-9082; Jeng, M. J. and Lemen, R. J. Am. Fam. Physician, 1997, 55(4): 1139-1146, 1149-1150).
RSV infection upregulates the expression of IL-1, IL-6, IL-8, TNF-, MIP1, RANTES, and ICAM-1 in epithelial cells, which are the main targets of RSV infection in vivo (Garofalo, R. et al. J. Immunol., 1996, 157(6): 2506-2513; Behera, A. K. et al. Biochem. Biophys. Res. Commun., 2001, 280(1): 188-195; Bitko, V. et al. Virology, 1997, 232(2): 369-378; Elias, J. A. et al. J. Biol. Chem., 1994, 269(35): 22261-22268). The elevated expression of these inflammatory molecules in RSV infection has been attributed to activation of nuclear factor-κB (Fiedler, M. A. et al. J. Virol., 1996, 70(12): 9079-9082; Garofalo, R. et al. J. Virol., 1996, 70(12): 8773-8781; Jamaluddin, M. et al. J. Virol., 1998, 72(6): 4849-4857; Bitko, V. and Barik, S. J. Virol., 1998, 72(7): 5610-5618).
The signal transducers and activators of transcription (STATs) mediate responses to diverse cytokine and non-cytokine stimuli, resulting in the altered expression of genes involved in inflammation (Bruder, J. T. and Kovesdi, I. J. Virol., 1997, 71(1): 398-404; Improta, T. and Pine, R. Cytokine, 1997, 9(6): 383-393; Durbin, J. E. et al. Cell, 1996, 84(3): 443-450). A number of viruses utilize the STAT pathway for gene activation through cell surface binding of viral proteins. Epstein-Barr virus-transformed lymphoblastoid cells and Friend leukemia virus-transformed erythroid cells exhibit a constitutively activated JAK-STAT pathway (Weber-Nordt, R. M. et al. Blood, 1996, 88(3): 809-816; Yamamura, Y. et al. Mol. Cell Biol., 1998, 18(3): 1172-1180), and the tyrosine kinase-interacting proteins of herpes virus saimiri and HIV induce the activation of a JAK-STAT cascade (Lund, T. C. et al. J. Virol., 1997, 71(9): 6677-6682; Molden, J. et al. J. Biol. Chem., 1997, 272(31): 19625-19631; Shrikant, P. et al. J. Immunol., 1996, 156(3): 1307-1314). However, STATs have not previously been implicated in RSV infection. It has been shown that RSV infection of epithelial cells leads to the induction of a variety of cytokines, chemokines, and adhesion molecules (Behera, A. K. et al. Biochem. Biophys. Res. Commun., 1998, 251(3): 704-709; Matsuse, H. et al. J. Immunol., 2000, 164(12): 6583-6592). The presence of STAT-1- and AP1-binding sequences in the promoters of RSV-inducible genes (ICAM-1, RANTES, and endothelin-1) (Behera, A. K. et al. Biochem. Biophys. Res. Commun., 2001, 280(1): 188-195) and the report that STAT-1 is constitutively expressed in asthmatics (Sampath, D. et al. J. Clin. Invest., 1999, 103(9): 1353-1361). However, it is not known whether RSV infection may activate STAT-1.
Based on the transfac promoter analysis of RSV-induced early genes identified in microarray studies, the present inventor postulated that RSV activates multiple signaling pathways in epithelial cells (Quandt, K. et al. Nucleic Acids Res., 1995, 23: 4878-4884; Kong, X. et al. Biochem. Biophys. Res. Commun., 2003, 306: 616-622). This analysis revealed binding sites for activator protein-1 suggesting that extracellular signal-regulated kinases (ERKs) may also be involved in early gene expression. ERK-1 and ERK-2 mediate specific responses to diverse stimuli, including viruses, cytokines, and growth factors and hormones (Li, J. D. et al. Proc. Natl. Acad. Sci. USA, 1998, 95: 5718-5723; Bruder, J. T. and Kovesdi, I. J. Virol., 1997, 71: 398-404; Jahnke, A. and Johnson, J. P. FEBS Lett., 1994, 354: 220-226; Garcia, R. et al. Cell Growth Differ., 1997, 8: 1267-1276; Improta, T. and Pine, R. Cytokine, 1997, 9: 383-393). RSV-induced production of IL-8 and RANTES is dependent on activated ERK-2 (Chen, W. et al. Exp. Lung Res., 2000, 26: 13-26; Pazdrak, K. et al. Am. J. Physiol., Lung Cell Mol. Physiol., 2002, 283:L364-L372). However, the role of ERKs in early signaling responses in RSV infection remains poorly understood. Also, whether interrupting ERK pathways can alter the course of viral infection is not known.